A system for an automatic transmission which transfers auxiliary power from a driving power source, such as an internal combustion engine and an electric motor, for another intended purpose is known. According to U.S. Pat. No. 5,522,778 corresponding to Japanese Patent Laid-Open Publication No. 1995-304348, this type of system for the automatic transmission houses an auxiliary driving gear which is configured to rotate in response to rotation of an automatic transmission input shaft. A power take-off device, i.e., a PTO device, can be operated when the auxiliary driving gear is engaged with a gear of the PTO device, thereby obtaining the auxiliary power for another intended purpose. In the system for the automatic transmission, the PTO device can be operated only while a shift lever has been moved to a neutral or parking position during an on operation of an on/off switch for operating the PTO device.
When a vehicle provided with an automatic transmission is moving forward, the rotational speed of the automatic transmission input shaft is transmitted to an output shaft after having been shifted to a predetermined speed change ratio in the transmission. Therefore, oil already introduced into the output shaft and other shafts rotatable only during the vehicle forward travel is applied with centrifugal force, and then will be supplied to the outer peripheral sides of these shafts. Generally, a bearing is provided between each shaft in the transmission, or between each gear component for a planetary gear set. Therefore, each bearing can be lubricated with the oil supplied to the outer peripheral side of these shafts.
However, when the vehicle is not moving, other shafts rotatable only during the vehicle forward travel and the output shaft are not rotated. Thus, the oil already guided into these shafts is not subjected to a centrifugal force. That is, the oil cannot be supplied to the outer peripheral sides of these shafts. In this case, if the PTO device is operated while the vehicle has been stationary—i.e., while the shift lever has been positioned at the neutral or parking position, each bearing may not be effectively lubricated with the oil.
A need thus exists for providing an improved lubricating system for an automatic transmission capable of sufficiently lubricating each bearing with oil when auxiliary power is needed even during a vehicle stationary condition.